Method and apparatus for heat conduction from a flat surface of a conductor on an electrical component



Feb. 2o, w68

R. w. DRONSUTH ETA'. 3,369,597 METHOD AND APPARATUS FOR HEAT CONDUCTION FROM A FLAT,

SURFACE OF A CONDUCTOR ON AN ELECTRCAL COMPONENT Filed June 18, 1965 2 Sheets-Sheet l as A80 90 60 /NVENTRS 63 R/CHARD w @ROA/50TH A @y mfom/ck L. H/rO/v Feb. 20, 1968 R W. DRoNsUTH ETAI. 3,369,597

METHOD AND APPAl'ATUS FOR HEAT CONDUCTION FROM A FLAT SURFACE OF A CONDUCTOR ON AN ELECTRICAL COMPONENT Filed June 18, 1965 2 Sheets-Sheet 2 /NVE/VTORS. R/CHAHD W. DRO/VSUTH gEDER/CK .H/LTO/V United States Patent Office 3,369,597 PatentedlF eb. 20, 1968 METHOD AND APPARATUS FOR HEAT CONDUC- TION FROM A FLAT SURFACE OF A CONDUC- TOR ON AN ELECTRICAL COMPONENT Richard W. Dronsuth, Westchester, andf Frederick L.

Hilton, Bensenville, Ill., assignors to Motorola, Inc.,

Franklin Park, Ill., a corporation of Illinois Filed June 18, 1965, Ser. No. 465,132 9 Claims. (Cl. 165-80) This invention pertains generally to a device for supporting and cooling an electron discharge device and more specifically to a device for cooling the anode and screen grid seals of a high power electron discharge tube.

In a high power radio transmitter the output electron discharge tube -dissipates substantial heat. It has been standard practice to provide a blower for circulating air over portions of the tube which' dissipates the heat. However, this adds to the cost and provides a moving part which is subject to failure and requires substantial maintenance. It is necessary to provide filters in the air stream and this presents a problem that the filters become clogged and suflicient air is not provided for adequate cooling.

In presently used high power tubes, the critical temperature of the tube beyond which failure occurs is determined by the critical temperatures of the anode and screen grid seals. In order-to insure adequate longevity and reliability of the tubes, it is necessary to maintain these seals at a temperature below their critical value. In transmitters having a blower, air is forced through veins in a member in thermal contact with the anode to remove the heat from the member thereby cooling the anode and associated seal. The air may also be passed over a member in thermal contact with the screen grid to cool the screen grid seal.

One object of this invention is to provide an improved device for supporting and cooling a high power electron discharge device.

Another object of this invention is to provide an improved device for supporting and cooling the anode, screen grid and associated seals of a high power output electron discharge tube, without the use of an air blowe which provides forced air cooling of the tube.

Still another object of this invention is to provide an improved device for supporting and cooling the elements of a high power output electron tube which develops substantial heat, and which is relatively compact and inexpensive to produce.

One feature of this invention is the provision of a device for supporting and cooling an electron discharge device which has a heat conduction member, having a clamp resiliently urging the conduction member against a heat conducting member which is also an electrical insulator and which is mounted to a heat sink thereby providing a heat conduction path from the conduction member to the heat sink for cooling the member.

Another feature of this invention is a device for supporting and cooling an electron discharge device, which provides a heat conducting path from the device to a heat sink, and with a chimney encompassing the heat sink through which air circulates for removing heat from the same.

Still another feature of the invention is a device for supporting and cooling the anode, screen grid and associated seals of a high power output electron discharge tube, which has a first heat conducting member providing a fioating support for the tube with an annular portion in thermal contact with the screen grid, and a second heat conduction member in thermal contact with the anode. The second heat conduction member has a flat heat conducting face engaging a fiat face on a heat conducting and electrical insulating member mounted to a heat sink, and a clamp cooperates with the oating support to resiliently press the flat face of 'the first heat conducting member into good thermal bond with the iiat insulating member to provide a heat conduction path for cooling the anode and associated seal. The first heat conducting member includes a pair of annular contact finger structures engaging the screen grid ring and providing a heat conduction path therefrom.

In the drawings:

FIG. 1 is a side elevation showing the mechanism of this invention;

FIG. 2 is a Plan View of the mechanism of FIG. l;

FIG. 3 is a cross-Section taken along the lines 3 3 of FIG. 1;

FIG. 4 is a cross-section taken along the lines 4 4 of FIG. 2;

FIG. 5 is an exploded perspective view of the mechanism of this invention;

FIG. 6 is a perspective View of the cabinet housing the mechanism of'FIG. 2;

FIG. 7 is a plan view of the bottom of the tube shown in FIG. l;

FIG. 8 is a plan view of the tube socket and mounting plate; and

FIG. 9 is an exploded perspective view of the tube socket and mounting plate shown in FIG. 7.

In a specific form of the invention, a high power output electron discharge tube has a first heat conducting member of substantial mass in thermal contact with the anode and associated seal, and a second member having an annular portion in thermal contact with the screen grid and associated seal. The tube is mounted in a socket in a mounting plate which has resilient fingers extending from the perimeter of the plate. These fingers provide a floating support for the plate and socket. A heat sink is provided which has heat radiating fins for removing the heat therefrom and a fiat protrusion to which is fixedly mounted a fiat electrical insulating and thermal conducting member. A releasable clamp resiliently urges a flat face of the first heat conducting member into good thermal bond with the fiat electrical insulating member thereby providing a heat conducting path from the anode and associated seal for cooling the same. A second heat sink is formed by coupling together a pair of plates each having an aperture with raised resilient fingers on the periphery thereof. The lingers form an annular groove, and when the plates are mounted to the tube mounting plate, the annular groove is aligned coaxially with the tube socket in the tube mounting plate. When the tube is inserted in the socket, the annular portion of the second member of the tube fits into the annular groove to provide a heat conduction path from the screen grid and associated seal through the resilient fingers to the plates for cooling the grid and seal.

Operation of a specific embodiment of the invention can best be understood by referring to the gures of the drawing. FIG. 1 shows the chassis 12 of a single ended power output stage of a radio transmitter. The transmitter could operate in any frequency band.l The power amplifier stage could operate either in push-pull with two high power output electron discharge tubes, or in single ended configuration with one high power output tube. In push-pull operation two tubes may have approximately a 600 watt input and a 400 watt output. This means that each tube would have to dissipate approximately watts in heat. In single ended operation the tube might have approximately a 200 watt input with a 100 watt output, with the tube dissipating approximately l0() watts in heat. Because the critical temperature of the power tube beyond which failure occurs is determined by the critical temperatures of the anode and screen grid seals of the tube, it is essential that these seals be maintained at temperature below their critical value during operation of the transmitter.

A high power output electron discharge tube is mounted in the chassis 12 in a manner to be ydescribed subsequently. The tube 20 has a termin-al 22 connected to the plate electrode-of the tube. Encircling the terminal 22 and in thermal contact with the plate electrode of the tube 20 is a first heat conducting member 25 made out of copper, lfor example, having considerable mass and a flat heat conducting face 27. A metallic seal 30, in contact with the plate, seals the space between the plate and the ceramic body 32 of the tube. A second heat conducting member 34 of metallic material encircles the base of the tube 20 and is in thermal contact with the screen grid of the tube. The member 34 (FIG. 7) has an annular groovcd portion 38 defined by the outer wall 40 and inner wall 42 of the member 34. A metallic seal 36, in contact with the screen grid, seals the space between the grid and the ceramic body 32.

The tube 20 is mounted in the chassis 12 on ioating support 45. The floating action of the support l45 is accomplished by fastening the resilient linger 47 along the perimeterof the support 45. When the support 45 is set into position on base 48, the tips of the fingers 47 will rest -on the base 48 and support the weight of the tube 20. The screws 50 are threaded to the base 48 and are tightened to a position where their heads contact the support 45 and apply tension to the tinge-rs 47. In this manner the suppolt 45 is positioned in a general area on base 48 but `still may be moved or floated as permitted by resilient action of the fingers.

A tube socket 55 (FIG. 8) is secured in the support 45 for receiving the terminal posts 56 of the tube 20 and extends through the base 48. The socket contains connections 58 (FIG. 3) for connecting the tube with the remaining components of the power output stage of the transmitter. A pair of plates 60 and 61 is mounted to the support 45 by screws 41 (FIG. 4) which are insulated from the plates by shoulder insulating washer 44 and are threaded into the tube socket mounting plate 43. The plates are separated from the support 45 by a mica sheet 63. The mica sheet 63 between the plate 60 and the support 45 forms a bypass capacitor for transient AC currents in the screen grid circuit. These are bypassed to ground as the support 45 is grounded to the chassis 12 through the resilient lingers 47.

Each of the plates has a round aperture in the center (FIG. 9), with the diameter of the aperture 65 in plate 61 being greater than the diameter of aperture 66 in plate '60. Encircling the apertures 65 and 66 at the periphery thereof a-re raised resilient lingers 68 and 69 (FIG. 4) respectively. The plates .are mounted with the aperture 65 being coaxial with the aperture 66 so that the raised resilient ngers 68 and 69 form an annular groove 70 (FIG. 8). When the plates a-re mounted to the support 45, the apertures are aligned with the socket 55 so that when `tube 20 is inserted in the socket the outer wall 40 of member 34 (FIG. 7) slips into the groove 70 and is held in place by the resilient action of the raised fingers 68. At the same time, the raised fingers 69 slip into the annular ygroove 3S in the member 34, with the wall 42 of that member .firmly positioned by the resilient action of the raised fingers 69. In this manner the tube 20 is held firmly in the support 45 and is free to float with it.

Now turning to the method used for cooling the tube as illustrated in FIGS. l through 5, a heat sink 80 made `out of aluminum, for instance, has heat radiating tins 82 as an integral part of the sink. The sink 80 is mounted .to the back 81 of chassis 12 by the screws 84 and has an integral protrusion 85 that extends through an opening 86 in the back 81. A flat heat conducting member 90 made out of beryllium oxide, for instance, which also manifests excellent electrical insulating properties is iixedly clamped to the protrusion 85 Iby clamps 92 which are secured to the heat sink 80 by screws 83. The member 90 4 should be suiiiciently thick to hold the electrical capaci-ty between the heat conducting face 27 of the tube 20 and the heat sink to a suitable low value.

In practice the releasable clamp 100 presses the iiat face 27 of the heat conducting member 25 into good thermal bond with the iiat electrical insulating member 90. To insure a good thermal bond, a coating of aluminum oxide-silicon grease 94, which exhibits good thermal conducting properties, is placed on the flat Vface surface 27 and on the fiat surface of member 90. It is at this point that the floating support 45 for the tube 20 finds its utility. As the clamp applies cross pressure to the member 25 to move it against the flat member 90, the resilient ngers 47 permit limited floating movement of the tube 20 and base 45 to insure that the liat face 27 is properly aligned to the flat surface of the member 90.

The particular releasable clamp used in this embodiment of the invention is of a standard type. It consists of a clamp bracket 102 secured to the base 4S of the chassis 12 by screws 104. The base 101of the bracket 102 has finger portions 103 which extend over the tube mounting plate 45 and cooperate with screws 50 to maintain tension on the plate 45. The bracket has a cl-amp plate supporting portion 105 from which has been stamped and bent into position above the supporting portion 105 two guide p-ieces 107. The clamp plate is slidably mounted on the support portion 105 and between the guide pieces 107. The clamp 100 is secured to the clamp plate 110 by the screws 112 (FIG. 2), and is of a width that permits it to slide between the guide pieces 107 with the plate 110. The clamp 100 is pivoted about a fixed point 120 (FIG. l) and is pivotally connected to an arcuate length 121 at 122. The end of the arcuate length 121 not pivotally connected to the clamp 100, is pivoted at 127 to the arm of the clamp 100. A cone shaped insulator 132 is secured to the end of the arm 130 and contacts the member 25 when the clamp is locked in place. A spring 115 made out of Phosphor bronze, for instance, is secured to the base 48 of the chassis 12 and extends upward through a slot 117 in the plate 110.

The clamp bracket 102 is positioned relative to the tube 20 on the chassis base 48 so that the arm 130 moves the member 25 into contact with liat insulator 90 before the cl-amp is locked. Continued pressure on the clamp causes the clamp plate 110 to slide against the pressure `of spring 115. When the pivot at 122 drops below the center line of pivots 127 and 120, the clamp is releasably locked into position, with the arm 130 resiliently pressing `face 27 against at insulator 90.

Moving the clamp to the lock position completes a heat conduction path from the plate through member 25, flat insulator 90 to the heat sink 80. The heat is then radiated from the heat radiating fins 82. A chimney (FIG. 6) which has an air inlet 11 in the back 15 of the cabinet 10 and an outlet 13 at the top 14 of the cabinet 10 encompasses the heat sink and ventilates the heat away from the tins 82 by convection. By cooling vthe plate electrode in this fashion, the associated metallic seal 30 is cooled below its critical temperature. Heat in excess of 100 watts may be removed from member 25 in this manner. Other means could be used for clamping the member 25 to the flat insulator 90 besides the described clamp; for instance, a screw could be moun-ted that could be turned to apply the desired pressure tov member 25.

The two plates 60 and 61, besides cooperating with the socket 55 for mounting the tube 20, form a second heat sink that is used to dissipate the heat from the screen grid seal and the base seal. The heat conduction path 1s from the screen grid to the member 34 through the resilient `fingers 68 and 69 to the plates 60 and 61. Since the amount of heat created at the screen grid is relatively Small cornpared to that at the plate, it is dissipated through radiation to the inside of the chassis 12 without using a chimney or other means to carry it outside the cabinet 10. The

second heat sink can dissipate heat from the member 34 in excess of watts.

FIG, 6 shows a cabinet 10 in which is rack mounted various units of a radio transmitter, however, only the chassis 12, which supports the power output stage of the transmitter, is shown. The back of the cabinet 10 is hinged at 16 and may be opened to provide access to the various units.

What has -been described, therefore, is an improved device for supporting and cooling an electronic discharge device that eliminates the use of an air blower for forced air cooling of the device and is relatively compact and inexpensive to produce.

We claim:

1. Apparatus for supporting and cooling an electron device which has a heat conduction member with a fiat heat conducting face, said device including in combination, mounting means for the electron device including a socket providing a floating support therefor, heat radiation means having heat conducting means with a fiat face mounted thereto for matingly engaging said fiat heat conducting face on said member, said heat conducting means being constructed of a material which forms an electrical insulator, and clamping means for engaging the electron device and resiliently urging the fiat heat conducting face of the member to close thermal contact with said fiat face of said heat conducting means thereby providing a heat conduction path from the heat conduction member for cooling the same.

2. A power output stage of a transmitting apparatus including in combination, an electron discharge device having an annular heat conduction member with a fiat heat conducting face, mounting means for said electron device including a socket providing a floating support therefor, heat radiation means having flat heat conducting means mounted thereto for matingly engaging said flat heat conducting face on said member, said heat conducting means being constructed of a material which forms an electrical insulator, and clamping means resiliently engaging said heat conduction member and urgingsaid fiat heat conducting face thereof into close thermal bond with said fiat heat conducting means, thereby providing a heat conduction path from said first conduction member for cooling the same.

3. A power output stage of a transmitting apparatus including in combination, an electron discharge device having an annular heat conduction member, with a fiat heat conducting face, mounting means for said electron device including a socket providing a floating support therefor, heat radiation means having a portion with a fiat heat conducting face for matingly engaging said flat heat conducting face on said member, said portion of said heat radiating means being constructed of a material which forms an electrical insulator, said heat radiation means including" a chimney for removing heat from the same, clamping means resiliently engaging said heat conducting member and urging said fiat face thereof into close thermal bond with said fiat heat conducting means thereby providing a heat conduction path from said conduction member for cooling the same.

4. An apparatus for supporting and cooling an electron discharge device which has annular rst and second heat conduction members, with the first member having a fiat heat conducting face, said apparatus including in combination, mounting means for the device including a socket providing a fioating support therefor, heat radiation means having flat heat conducting means mounted thereto for matingly engaging said fiat heat conducting face on said first member, said heat conducting means being constructed of a material which forms an electrical insulator, clamping means resiliently engaging the first heat conducting member and urging said fiat face thereof into close thermal bond with said flat heat conducting means, thereby providing a heat conduction path from the first conduction member for cooling the same, second heat radiation means supported by said tube mounting means and including a pair of annular rings cooperating with said socket for receiving the second heat conduction member and providing a heat conduction path therefrom.

5. A power output stage of a transmitting apparatus including in combination an electron discharge device having annular first and second heat conduction members, mounting means for said device including a socket providing a fioating support therefor, first heat radiation means having heat conducting means mounted thereto for engaging the first heat conduction member, said heat conducting means being constructed of a material which forms an electrical insulator, clamping means resiliently engaging said first heat conducting member and urging the same into engagement with said heat conducting means thereby providing a heat conduction path from said first conduction member for cooling the same, said first heat radiation means including a portion with heat radiating fins extending therefrom, means including a chimney encompassing said heat radiating fins for removing heat from the same, second heat radiation means supported by said tube mounting means and including a pair of annular rings cooperating with said socket for receiving said second heat conduction member and providing a heat conduction path therefrom.

6. An appanatus for supporting and cooling an electron discharge device which has annular first and second heat conduction members, said device including in cornbination, mounting means for the device including a socket providing a floating support therefor, Afirst heat radiation means having heat conducting means mounted thereto for engaging the first heat conduction member, said heat conducting means being constructed of a material which forms an electrical insulator, clamping means resiliently engaging the first heat conduction member and urging the same into engagement with said heat conducting means thereby providing a heatconduction path from the first conduction member for cooling the same, `second heat radiation means supported by said tube mounting means and including a pair of annular rings cooperating with said socket for receiving the second heat conduction member and providing a heat conduction path therefrom.

7. A device for supporting and cooling the anode and screen grid and associated seals of a high power output electron discharge tube, including in combination, a first annular member in thermal contact with the anode having a substantial mass and a fiat heat conducting face, a second member having an annular portion and in thermal contact with the screen, a tube mounting plate having a socket to receive the tube and resilient fingers extending in a `direction from the perimeter of said plate to provide a floating support for said socket and the tube, a first heat sink having a fiat faced protrusion and a portion with radiating fins extending therefrom, a fiat electrical insulating and thermal conducting member attached to said first heat sink and mated to said flat faced protrusion, a releasable clamp for resiliently engaging said first member and pressing said fiat heat conducting face of same into close thermal bond with said flat member, a first heat conducting path for cooling the anode including said first member, said :dat memberfand said first heat sink, a chimney encompassing said radiating tins for removing the heat from the same, a second heat sink including first and second plates, said first plate having a round aperture having raised resilient fingers at the periphery thereof, said second plate having a round apertura with a diameter less than the diameter of said first round aperture and havking raised resilient fingers at the periphery thereof, an

annular groove delimited by said fingers and formed by said second aperture and plate being concentrically mounted to said first aperture and plate, said first and second plates mounted to said tube mounting plate with a dielectric therebetween and having said apertures coaxial with said socket, said annular portion of said second member fitting into said annular groove with the tube mounted in said socket to form a second heat conducting path for cooling the screen including said second mass, said first groove, said raised fingers and said first and second plates.

8. The method of cooling an electron device which has an annular heat conduction member having a ilat heat conducting face including the steps of mounting the device on a floating support, mounting a at heat conducting and electrical insulating member to a heat sink, and resiliently engaging said heat conduction member to cause said at heat conducting face thereof to engage said flat heat conducting and electrical insulating member to transfer heat to the heat sink.

9. The method of cooling an electron discharge device which has annular first 'and second heat conduction members, with the first member having a at heat conducting face including the steps of mounting the device in a socket on a floating support, mounting a flat heat conducting and electrical insulating member to a heat sink, resiliently engaging said rst heat conduction member to clamp said flat heat conducting face thereof to said at heat conducting and electrical insulating member, mounting a second heat sink to said floating support, and placing the annular portion of the second member into contract with a pair of annular rings connected to said second heat sink.

References Cited UNITED STATES PATENTS 2,506,733 5/1950 Nergaard 313-45 X 2,605,439 7/1952 Boyer et al 313-40 X 3,043,973 7/1962 Deserno et al 313-46 X 3,226,542 12/1965 Craig et al. 313-46 X 3,261,904- 7/1966 Wulc 174-15 3,264,534 8/1966 Murphy 317--100 X 3,267,333 `8/1966 Schultz 317--100 3,293,508 12/1966 Boyer 317--234 FOREIGN PATENTS 1,184,000 12/ 1964 Germany.

633,376 12/ 1949 Great Britain.

EDWARD I. MICHAEL, Primary Examiner'.

A. W. DAVIS, JR., Assistant Examiner. 

8. THE METHOD OF COOLING AN ELECTRON DEVICE WHICH HAS AN ANNULAR HEAT CONDUCTION MEMBER HAVING A FLAT HEAT CONDUCTING FACE INCLUDING THE STEPS OF MOUNTING THE DEVICE ON A FLOATING SUPPORT, MOUNTING A FLAT HEAT CONDUCTING AND ELECTRICAL INSULATING MEMBER TO A HEAT SINK, AND RESILIENTLY ENGAGING SAID HEAT CONDUCTION MEMBER TO CAUSE SAID FLAT HEAT CONDUCTING FACE THEREOF TO ENGAGE SAID FLAT HEAT CONDUCTING AND ELECTRICAL INSULATING MEMBER TO TRANSFER HEAT TO THE HEAT SINK. 